In recent years, there has been an increasing demand that the surface of substrates such as plastic surfaces and glass surfaces be more resistant to fogging and fouling.
To solve the fogging problem, antifogging coatings have been presented which include an acrylic oligomer and a reactive surfactant. Cured products obtained from such antifogging coatings (for example, films including the cured products) are reported to have enhanced hydrophilicity and water absorption (Non Patent Document 1). To solve the fouling problem, attentions have been drawn to, for example, anti-contamination materials which exhibit self-cleaning properties (anti-contamination properties) as a result of the enhancement in surface hydrophilicity so that fouling (such as airborne hydrophobic substances) which have become attached to surfaces such as exterior walls can be detached and removed efficiently from the surfaces by rainfall, water spray or the like (Non Patent Documents 2 and 3).
To solve these “fogging” and “fouling” problems, the present inventors have presented cured products (for example, monolayer films) which have anionic hydrophilic groups enriched (concentrated) at a surface (Patent Document 1). Cured products (for example, films) obtained according to this invention are transparent and highly hydrophilic, have excellent antifogging properties, antifouling properties, antistatic properties, quick dry properties (can remove water at a high rate) and chemical resistance, and are also hard and highly resistant to scratches. However, studies by the present inventors have revealed that abrasion resistance and weather resistance are still to be improved.
In general, coating the surface of a substrate with an inorganic compound is known as a method to impart enhanced weather resistance and abrasion resistance to the substrate surface. A typical example is the sol-gel reaction of an alkoxysilane to form a hard coat on a spectacle lens (Non Patent Document 4).
Alkoxysilane hard coats have a dense structure and are therefore very hard and as resistant to abrasion as glass. On the other hand, such hard coats have drawbacks such as that they are fragile, hard to dye and fogged easily and that fouling becomes attached easily and tends to remain persistently.
Various techniques have been presented to overcome such problems. For example, dyeing properties and toughness are imparted by blending a hydroxysilane with a melamine resin and an epoxy group-containing silicon compound (Patent Document 2), by adding an epoxy compound and an aluminum complex to a hydroxysilane (Patent Document 3), or by blending a hydroxysilane with a hydroxyl group-containing acrylic polymer (Patent Document 4).
Antifogging properties are imparted by blending an alkoxysilane with a styrenesulfonic acid polymer (Patent Document 5).
Further, a water-dispersible resin composition for coating steel plates is known which is obtained by blending a copolymer resin (A) with a zirconium compound (B) and a silane coupling agent (C) wherein the copolymer resin is obtained by the emulsion polymerization of an epoxy group-containing polymerizable unsaturated monomer, a polymerizable unsaturated monomer having an acid group such as sulfonic group, a hydroxyl group-containing polymerizable unsaturated monomer, and a polymerizable unsaturated monomer having a hydrolysable silyl group each in an amount of 0.1 to 10 wt % relative to the total weight of the monomers (Patent Document 6).
Similarly, a water-dispersible resin treatment agent for metal surfaces is known which is obtained by blending a core-shell resin (A) with a zirconium compound (B) and a silane coupling agent (C) wherein the resin is obtained by the emulsion polymerization of a polymerizable unsaturated monomer having no epoxy groups, acid groups or hydroxyl groups, an epoxy group-containing polymerizable unsaturated monomer, a polymerizable unsaturated monomer having an acid group such as sulfonic group, a hydroxyl group-containing polymerizable unsaturated monomer, a polymerizable unsaturated monomer having a hydrolysable silyl group, and a polymerizable unsaturated monomer having cyclic ureido group with the specific structure each in an amount of 0.1 to 5 wt % relative to the total weight of the monomers (Patent Document 7).
Further, a method has been disclosed in which highly hydrophilic cured films are obtained by reacting a copolymer having a sulfonate group and an alkoxysilyl group, with an alkoxysilane (Patent Document 8). Furthermore, the present inventors have presented a method for obtaining highly hydrophilic cured films by reacting a copolymer having a sulfonate group and an epoxy group, with an alkoxysilane (Patent Document 9).